There has been known a device for detecting capacitance values distributed in a matrix. Patent Literature 1, for example, discloses a capacitance detecting device for detecting distribution of capacitance values of a capacitor matrix formed between M drive lines and L sense lines. According to the capacitance detecting device, in a case where a touch panel is touched with a finger or a pen, a touched capacitor has a reduced capacitance value. This causes the capacitance detecting device to detect a change which reduced a capacitance value, so as to detect the touch with the finger or the pen.
FIG. 21 is a view schematically illustrating a configuration of a conventional touch panel system 91. FIG. 22 is a view for explaining a method for driving the touch panel system 91. The touch panel system 91 includes a touch panel 92. The touch panel 92 includes drive lines DL1 through DL4, sense lines SL1 through SL4, and capacitors C11 through C44 provided at intersections of the drive lines DL1 through DL4 and the sense lines SL1 through SL4.
The touch panel system 91 includes a driving section 94. The driving section 94 drives the drive lines DL1 through DL4 in accordance with a code sequence with 4 rows and 4 columns which code sequence is represented by EXPRESSION 3 of FIG. 22. The driving section 94 applies a source voltage VDD in a case where an element of the code sequence is “1”. Meanwhile, the driving section 94 applies zero volt in a case where the element of the code sequence is “0”.
The touch panel system 91 includes four amplifiers 98 provided so as to correspond to the respective sense lines SL1 through SL4. The amplifiers 98 (i) receive respective linear sums Y1, Y2, Y3, and Y4 of capacitances of capacitors which are driven by the driving section 94 and are provided along the respective sense lines SL, and (ii) amplify the linear sums Y1, Y2, Y3, and Y4.
For example, during the first driving of four times of driving in accordance with the code sequence with 4 rows and 4 columns, the driving section 94 applies the source voltage VDD to the drive line DL1, and applies zero volt to each of the remaining drive lines DL2 through DL4. Then, for example, an output corresponding to the capacitor C31 and represented by EXPRESSION 1 of FIG. 22 is supplied, as the measured value Y1, from the sense line SL3 to a corresponding amplifier 98.
During the second driving, the driving section 94 applies the source voltage VDD to the drive line DL2, and applies zero volt to each of the remaining drive lines DL1, DL3, and DL4. Then, an output corresponding to the capacitor C32 and represented by EXPRESSION 2 of FIG. 22 is supplied, as the measured value Y2, from the sense line SL3 to a corresponding amplifier 98.
During the third driving, the driving section 94 applies the source voltage VDD to the drive line DL3, and applies zero volt to each of the remaining drive lines. During the fourth driving, the driving section 94 applies the source voltage VDD to the drive line DL4, and applies zero volt to each of the remaining drive lines.
This causes the measured values Y1, Y2, Y3, and Y4 themselves to be associated with the respective capacitance values C1, C2, C3, and C4 (see EXPRESSION 3 and EXPRESSION 4 of FIG. 22).